9月2日 复旦大学李世燕教授学术报告：Quantum transport and pressure study of Dirac/Weyl semimetals报告题目：Quantum transport and pressure study of Dirac/Weyl semimetals 时间：9月2日（周二） 下午15:00 地点：唐楼A213 摘要： Quantum transport and pressure study of Dirac/Weyl semimetals Shiyan Li Department of Physics, Fudan University We report the quantum transport properties of Cd3As2 single crystals in a magnetic field. A large linear magnetoresistance is observed near room temperature. With decreasing temperature, the Shubnikov-de Haas oscillations appear in both the longitudinal resistance Rxx and the transverse Hall resistance Rxy. From the strong oscillatory component ΔRxx, a linear dependence of the Landau index n on 1/B is obtained, and it gives an n-axis intercept between 1/2 and 5/8. This clearly reveals a nontrivial π Berry’s phase, which is a distinguished feature of Dirac fermions. Our quantum transport results provide bulk evidence for the existence of a three-dimensional Dirac semimetal phase in Cd3As2 [1]. Interestingly, we observe pressure-induced superconductivity in Cd3As2 under pressure above 8.5 GPa[2], while for the Weyl semimetal NbAs, the crystal structure remains stable and no superconducting transition is observed under pressure up to 20 GPa [3]. We will also present quantum transport study of WTe2 single crystals under ambient and high pressure, in which extremely large magnetoresistance (XMR) was discovered recently. By analyzing the Shubnikov-de Haas oscillations, four Fermi surfaces are identified for the first time, and two of them are found to persist to high pressure. The sizes of these two pockets are comparable, but show increasing difference with pressure. At 0.3 K and in 14.5 T, the magnetoresistance decreases drastically from 1.25 ´ 105% under ambient pressure to 7.47 ´ 103% under 23.6 kbar, which is likely caused by the relative change of Fermi surfaces. These results support the scenario that the perfect balance between the electron and hole populations is the origin of the XMR in WTe2 [4]. [1] L. P. He, X. C. Hong, J. K. Dong, J. Pan, Z. Zhang, J. Zhang, and S. Y. Li, “Quantum transport evidence for the three-dimensional Dirac semimetal phase in Cd3As2”, Phys. Rev. Lett. 113, 246402 (2014). Editors’ Suggestion. [2] L. P. He, Y. T. Jia, S. J. Zhang, X. C. Hong, C. Q. Jin, and S. Y. Li, “Pressure-induced superconductivity in the three-dimensional Dirac semimetal Cd3As2”, arXiv:1502.02509. [3] J. Zhang, F. L. Liu, J. K. Dong, Y. Xu, N. N. Li, W. G. Yang, and S. Y. Li, “High-pressure study of the Weyl semimetal NbAs”, CPL 32, 097102 (2015). [4] P. L. Cai, J. Hu, L. P. He, J. Pan, X. C. Hong, Z. Zhang, J. Zhang, J. Wei, Z. Q. Mao, and S. Y. Li, “Drastic pressure effect on the extremely large magnetoresistance in WTe2: quantum oscillation study”, Phys. Rev. Lett. 115, 057202 (2015). ---------------------------------------------------------------- 报告人简介： 李世燕，1997和2002年在中国科技大学物理系获得学士和博士学位。2002-2007年在加拿大多伦多大学和Sherbrooke大学做博士后。2007年任复旦大学先进材料实验室研究员，2012年任复旦大学物理系“谢希德”青年特聘教授。受教育部“新世纪优秀人才支持计划”、基金委优秀青年基金、上海市东方学者、上海市优秀学术带头人等人才计划支持。主要开展关联电子体系的极低温电、热输运及高压下的性质研究，重点研究超导体、量子磁体、拓扑材料等。发表SCI论文六十余篇，其中包括Physical Review Letters十一篇，Physical Review X两篇，Nature Physics一篇，Nature Nanotechnology一篇，Nature Communications一篇，论文共被引用约1380次。 |
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电话：+86 25 83592756 传真：+86 25 83595535
